Bunny Rabbit Goonie -- Part 6: Ears and Motor Mount
The Thrifty Rocketeer blog continues...
This should be the final entry in this build thread. I can't believe that I have to show how to cut and attach ears to a bunny nose cone, but some people have asked.
Plus, because you demanded it: How to assemble a motor mount assembly for the Baby Bertha rocket we are using.
First, I photocopied the plans and then cut out the ear templates. Now, if you can photocopy onto card stock, you can skip a step. But I couldn't.
So I traced the shape onto a spare 3"x5" index card, with the intent to use the blank side.
After trimming the excess off, I sketched in the soft pink interior part of the ear, but to my dismay, the dry erase red marker I chose had dried out and would only give me a soft pink smudge after several passes.
To my mistake, I didn't leave well enough alone, but traced the shape in red pen and tried another dry erase marker. THIS one bled red, just as you might think a marker would. I should have left well enough alone. But I didn't. I decided to make both look the same, and figured the accent color of red would help me find the ear if it flies off during launch or recovery.
Finally, I used a drop of Testor's plastic model cement to try to attach them to the nosecone, ABOVE the shoulder that will drop into the body tube. My tube of glue has just about turned over, so I doubt this set of ears will adhere well. I'll probably be doing this again later.
And now, the moment you've all been waiting for....
No, not the finished face, but the creation of the motor mount.
There are six small steps here.
First, I freed all the elements from their plastic bag. Note, the launch lug also came in the bag, and the metal spring clip was packaged with the shock cord and parachute, but I've gathered them all here.
I measured 1/2", 1 1/4" and 2 1/2" from the left end and made a mark.
You are supposed to use the point of your Exacto knife to make a small slice at 2 1/2" mark 1/8" wide, just enough to accept the end of the metal spring. I forgot my knife, so I just pressed and wiggled the end to punch through the thin motor mount tube. It worked. It will be sealed and strengthened by some wood glue two steps later down.
Next, the thin plastic ring slips easily over the motor mount tube, and the metal spring from the right stopping just about the width of the ring above the 1 1/4" mark. A thin but complete ring of wood glue is applied around the outside of the tube at that 1 1/4" mark.
Immediately upon smoothing the glue out, I slid the plastic ring into that glue. (Some glue will squeegee away ahead of the ring, but some remains on the tube.) Position the ring at that 1 1/4" mark and let dry. (Note, to keep the tube from rolling, I have parked the launch lug next to the tube temporarily. It will not stay.)
The ring motor block will go inside the motor mount tube and be stopped by the lip of the metal spring. But first we spread a ring of wood glue inside the right end of the motor mount tube, all around and onto the tab of the metal spring clip where it will anchor it. It's not hard to insert the green motor block and it rests against the metal tab when in position. Let dry.
In the meantime, cut out or punch out carefully the two centering rings. One has an extra notch in the inside circle. This will allow the metal spring to flex. The other does not. Slip the ring without the notch just over the right end of the motor mount tube and then apply a glue fillet to both sides.
Slip the notched ring over the left end of the tube, with the metal spring aligned in the notch. Slide the ring up to the 1/2" mark and when perpendicular, spread a ring of glue on both sides to hold it in place. DO NOT SEAL THE NOTCH. DO NOT GLUE THE METAL SPRING DOWN. So, you've not quite circled the tube with a band of glue. It's more of a "C" of glue, leaving the spring free to flex. Set the entire complete motor mount assembly aside to dry completely, before attempting to insert.
Once dry, spread a ring of glue 2" deep inside the body tube on the fin end. This ring of glue will squeegee a little as the motor mount forward ring comes in contact with it. You want just enough to form a ring of glue around the outer edge of the centering ring, securing it to the body tube when dry. You DO NOT want so much that the glue flows over the open motor mount tube nor seals the hole in motor block ring .
Some people try to add a ring of glue inside the body tube after the forward ring is halfway up the tube (but not yet into its glue) so that there will be a second ring or puddle of wood glue for the rear centering ring to squeegee and settle into. This is tricky work, but can be done.
Alternatively, push the motor mount forward into the forward glue ring, just far enough that the tail pipe of the motor mount becomes flush with the bottom of the body tube. Set aside for the forward ring to dry before upending the body tube and adding a fillet of glue externally to the rear centering ring. You want just enough to contact the centering ring and the body tube and form a fillet. DO NOT FILL THE WELL WITH GLUE, as it will add a lot of weight to your rocket.
So, there you have it, the assembly of the motor mount and generic instructions on how to insert. You could have done this before attaching the rear fins to the body tube, and been able to manhandle the body tube. But if you plunged ahead and attached the fins first, your grip and purchase to hold the body tube may be reduced...but it's not impossible.
As always when working with wood glue, you want just enough to contact the surface your want to glue, but not run. You can keep the glue from running by positioning the rocket or parts so the glue will puddle in place for 15-30 minutes before turning the rocket and risking the glue running.
If you have questions, ask me.
And don't forget to cap your glue when not in use, and save your scrap balsa... you never know when you're going to need some!
This should be the final entry in this build thread. I can't believe that I have to show how to cut and attach ears to a bunny nose cone, but some people have asked.
Plus, because you demanded it: How to assemble a motor mount assembly for the Baby Bertha rocket we are using.
First, I photocopied the plans and then cut out the ear templates. Now, if you can photocopy onto card stock, you can skip a step. But I couldn't.
So I traced the shape onto a spare 3"x5" index card, with the intent to use the blank side.
After trimming the excess off, I sketched in the soft pink interior part of the ear, but to my dismay, the dry erase red marker I chose had dried out and would only give me a soft pink smudge after several passes.
To my mistake, I didn't leave well enough alone, but traced the shape in red pen and tried another dry erase marker. THIS one bled red, just as you might think a marker would. I should have left well enough alone. But I didn't. I decided to make both look the same, and figured the accent color of red would help me find the ear if it flies off during launch or recovery.
Finally, I used a drop of Testor's plastic model cement to try to attach them to the nosecone, ABOVE the shoulder that will drop into the body tube. My tube of glue has just about turned over, so I doubt this set of ears will adhere well. I'll probably be doing this again later.
And now, the moment you've all been waiting for....
No, not the finished face, but the creation of the motor mount.
There are six small steps here.
First, I freed all the elements from their plastic bag. Note, the launch lug also came in the bag, and the metal spring clip was packaged with the shock cord and parachute, but I've gathered them all here.
I measured 1/2", 1 1/4" and 2 1/2" from the left end and made a mark.
You are supposed to use the point of your Exacto knife to make a small slice at 2 1/2" mark 1/8" wide, just enough to accept the end of the metal spring. I forgot my knife, so I just pressed and wiggled the end to punch through the thin motor mount tube. It worked. It will be sealed and strengthened by some wood glue two steps later down.
Next, the thin plastic ring slips easily over the motor mount tube, and the metal spring from the right stopping just about the width of the ring above the 1 1/4" mark. A thin but complete ring of wood glue is applied around the outside of the tube at that 1 1/4" mark.
Immediately upon smoothing the glue out, I slid the plastic ring into that glue. (Some glue will squeegee away ahead of the ring, but some remains on the tube.) Position the ring at that 1 1/4" mark and let dry. (Note, to keep the tube from rolling, I have parked the launch lug next to the tube temporarily. It will not stay.)
The ring motor block will go inside the motor mount tube and be stopped by the lip of the metal spring. But first we spread a ring of wood glue inside the right end of the motor mount tube, all around and onto the tab of the metal spring clip where it will anchor it. It's not hard to insert the green motor block and it rests against the metal tab when in position. Let dry.
In the meantime, cut out or punch out carefully the two centering rings. One has an extra notch in the inside circle. This will allow the metal spring to flex. The other does not. Slip the ring without the notch just over the right end of the motor mount tube and then apply a glue fillet to both sides.
Slip the notched ring over the left end of the tube, with the metal spring aligned in the notch. Slide the ring up to the 1/2" mark and when perpendicular, spread a ring of glue on both sides to hold it in place. DO NOT SEAL THE NOTCH. DO NOT GLUE THE METAL SPRING DOWN. So, you've not quite circled the tube with a band of glue. It's more of a "C" of glue, leaving the spring free to flex. Set the entire complete motor mount assembly aside to dry completely, before attempting to insert.
Once dry, spread a ring of glue 2" deep inside the body tube on the fin end. This ring of glue will squeegee a little as the motor mount forward ring comes in contact with it. You want just enough to form a ring of glue around the outer edge of the centering ring, securing it to the body tube when dry. You DO NOT want so much that the glue flows over the open motor mount tube nor seals the hole in motor block ring .
Some people try to add a ring of glue inside the body tube after the forward ring is halfway up the tube (but not yet into its glue) so that there will be a second ring or puddle of wood glue for the rear centering ring to squeegee and settle into. This is tricky work, but can be done.
Alternatively, push the motor mount forward into the forward glue ring, just far enough that the tail pipe of the motor mount becomes flush with the bottom of the body tube. Set aside for the forward ring to dry before upending the body tube and adding a fillet of glue externally to the rear centering ring. You want just enough to contact the centering ring and the body tube and form a fillet. DO NOT FILL THE WELL WITH GLUE, as it will add a lot of weight to your rocket.
So, there you have it, the assembly of the motor mount and generic instructions on how to insert. You could have done this before attaching the rear fins to the body tube, and been able to manhandle the body tube. But if you plunged ahead and attached the fins first, your grip and purchase to hold the body tube may be reduced...but it's not impossible.
As always when working with wood glue, you want just enough to contact the surface your want to glue, but not run. You can keep the glue from running by positioning the rocket or parts so the glue will puddle in place for 15-30 minutes before turning the rocket and risking the glue running.
If you have questions, ask me.
And don't forget to cap your glue when not in use, and save your scrap balsa... you never know when you're going to need some!
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